Catnip, (Nepeta cataria, Fam. Lamiaceae), an aromatic herb from southwestern Asia, is best known for causing a euphoric effect on domestic cats and other members of the feline family due to nepetalactone, a volatile compound contained in the essential oil of the plant. The aromatic volatiles of catnip are produced in the glandular trichomes in the leaf epidermis. Because of the morphological nature of the bilabiate bisexual flowers, this plant can self-pollinate and also has the ability to outcross. Current production methods utilize seeds and transplants from undomesticated populations. While normally cultivated for the pet toy industry as a safe attractant to cats and for ornamental applications, recent research has shown that essential oils from catnip are also an efficient insect repellent and are at least comparable to the industry standard repellent DEET with far less toxicity.
Catnip's volatile oil effectively repels mosquitoes, including the females that carry the plasmodium causing malaria and those that transmit yellow fever, filariasis, the West Nile virus, and encephalitis, for a total of six different mosquito species repelled. In one study, 41 different plant species were tested for repellency toward three species of mosquitos that carry pathogens, with N. cataria being one of the top five plants whose oil exhibited repellency.
One isomer of nepetalactone, the Z, E isomer, can be hydrogenated to form dihydronepetalactone 2, which is as effective at repelling two species of mosquitoes as DEET and offers complete protection for up to five hours, based on experiments involving human subjects. The Z, E isomer has also shown significant repellency towards house and stable flies, and it has also been reported that catnip-derived nepetalactones are an oviposition repellent. The peach-potato aphid is also repelled by nepetalactones, suggesting that N. cataria could be evaluated as an organic pesticide for peach orchards and potato fields. In addition, both the American and German cockroach, which harbor disease causing organisms, were repelled by the nepetalactones present in Nepeta cataria and showed better repellency than DEET. Common brown ticks and the deer tick that harbors the bacterium responsible for Lyme disease are repelled by the nepetalactones in N. cataria as well as the dihydronepetalactones. Three species of subterranean termites that cause damage to homes and other various wood-based structures resulting in significant financial loss were also repelled by the nepetalactones found in catnip oil. The Z, E nepetalactone isomer was also efficient in repelling many common house dust mite species, as well as poultry mites. In a body contact assay involving harvester ants, mortality was achieved faster with the Z, E nepetalactone isomer than the other nepetalactones in catnip.
Catnip is largely undomesticated, and little breeding has been undertaken to improve the plant's horticultural traits. The present inventors have undertaken genetic collections of catnip (Nepeta cataria) and related species sometimes known as catmint (Nepeta spp.) including accessions, unimproved lines/populations, and commercial varieties. The purposes of that initial work was to chemically characterize, identify, and develop production systems for commercial farmers and home gardeners to have access to a wide range of catnips that vary in their growth habit or morphology, chemistry, aromatic volatiles, and medicinal applications, including their non-volatile medicinal or bioactivity, and ornamental qualities. In 2004, the inventors began to select and improve catnip for its essential oil yields, growth and production performance and for its essential oil chemistry. Relative to most other members of the Lamiaceae family, catnip is susceptible to diseases and environmental stress, including poor winter survival in northern temperate zones. Tolerant plants can be used as perennials, although they are treated as annuals in commercially grown fields. Commercial fields from transplants are more expensive, as the labor cost is greater and the process is more difficult due to plants dying off and producing less biomass. Further, catnip exhibits a phenotypic architecture that does not lend itself to efficient mechanization. Catnip also produces lower essential oil yields compared to peppermint and spearmint, which have copious amounts of aromatic oils that can be commercially harvested mechanically. The commercialization of catnip as a source for above-ground biomass, essential oils, and isolated Z, E nepetalactone for new insect repellent products remains challenging.